First off, I went through Dial-Up Hell this weekend all because a few clouds hovered overhead, so I'm a bit pissy right now.
My opinion of Sith (which I saw last night) isn't quite formed, which means another viewing will be required. That's usually a good sign from moi: if I want to see it again to form a definite opinion, usually it will end up favorably. But for now, I can only offer my first impressions:
The final of the original "prequel" certainly lived up to the reviews of it being "darker". There was less exposition in this one than in the first two, but I felt like I needed a degree in Poli Sci in order to understand the crawl at the beginning. 
The whole "turning" of Anakin was nicely done (you knew it was coming, you just never knew why before). He actually was conflicted about it, it wasn't a "okay, now I'm a baddie". Plus, you got the whole notion that Anakin and Palpatine were at odds even from the beginning (right away, he was looking to off the emperor and take control. That seems to be big with the bad guys in Star Wars, kinda like the Mob) 
Thank god there was no Jar-Jar 
This certainly exceeded the previous two of the prequel trilogy (though I was more than willing to give the second a positive review because it worked in spite of itself), but I'm not sure it is worthy of comparisons to the originals. "Empire" is certainly its immediate forefather, but I think it'd be fairer to say that it's "Return of The Jedi" with the decisions reversed.
And that's my take for now 